11 - Storage Tanks and Tank Farms

Abstract

The external cathodic protection of underground storage tanks, particularly older tank installations, presents difficulties compared with buried pipelines. The tanks are often close to buildings or grouped close together. In many cases, buffed storage tanks are mounted on large concrete foundations as a protection against buoyancy. The preparatory work for tank installations with single-wall containers begins with checking whether cathodic protection is prescribed or is appropriate on the grounds of economy. Magnesium anodes are generally used for cathodically protected buried storage tanks with galvanic anodes. In addition, cathodic protection of the interior of flat-bottomed tanks is possible if the medium is conducting. Segregation of water can occur at the bottom of fuel tanks with constituents (salts, e.g., chloride) that lead to corrosion attack. This corrosion at the bottom of tanks can be prevented by cathodic protection in the design according to DIN 4119, if the electrolyte covers the bottom of the tank to a sufficient depth. Fuel producers and suppliers usually prevent access of electrolyte solutions because they see it dangerous for the purity of the oil according to DIN 51603 and they fear the damage to the heating circuit. However, damage caused by introducing electrolyte solutions or by the reaction products of cathodic protection has not been observed to date.